Large numbers of articles such as cans, bottles and other such cylindrical or curvilinear containers are conventionally palletized in a rapid and mechanized manner. This system is ubiquitous in industries where transport of unit loads is required. Generally a pallet is a flat transport structure which provides stability and supports unit loads while being lifted by a forklift or other jacking device. It is also common in industries where unit loads are transported in containers to a destination. Pallets are usually wooden, but can also be constructed of plastic or other materials. Each material in the current art is selected for varying properties and purposes. The term “palletized” has come to mean the mounting of the desired articles, or load, atop a wooden pallet. Optionally, the articles are fixed to the pallet by a fastening means such as shrink wrap or straps.
Palletizing articles generally involves an accumulator belt which delivers the articles to a tier forming area. The articles are then conveyed onto the pallet until the pallet is substantially filled with the articles-thereby forming a tier. The tiers, or layers, of articles are generally arranged to form transverse rows of differing, usually alternating orientations. Accordingly, the natural arrangement of a tier is to form the initial transverse row in the tier of one orientation with the next row having a second orientation.
After the first layer of articles are placed upon the pallet, the pallet is then lowered approximately the height of the article. A separator sheet is then disposed upon the assembled layer of articles. Additional articles are then conveyed onto the separator sheet to form another tier of articles. This operation is repeated until a multi-tier load is formed.
This form of palletization is quite common in manufacturing operations. The patterns of tiers are carefully predetermined for the purpose of economical utilization of space and for proper interfacing with subsequent operations. It is not unusual for such palletized loads to extend up to ten or fifteen feet in height. Accordingly, it is most important that each tier be properly positioned and oriented both in relationship to other tiers and to the pallet.
The articles (or packages of merchandise or products) that are conventionally loaded onto such pallets are then generally secured to the pallet for transportation. One method employed to secure individual packages or containers on a pallet is to bind them horizontally and vertically with metal bands or the like. For example, one approach is to enclose article-loaded pallets with loosely fitting bags of heat-shrinkable plastic film. Exposing the heat-shrinkable plastic film to a suitable heat treatment will cause the film to shrink into conforming engagement with the articles. Although this approach can also be utilized to secure the articles on a pallet without the need for straps or bands, the machinery necessary for heating the film enclosed pallet is rather bulky and expensive to operate. In addition, this approach is limited to articles that are not susceptible to heat damage during the film shrinkage process.
Another manner to secure pallatized articles is to tension wrap polyethylene stretch film around the articles until at least a thickness of several layers is achieved and then heat seal the trailing edge of the film to the underlying film wraps. This process requires a means for first securing the leading edge of the film to the article-loaded pallet and then heating means to secure the trailing edge of the film to an area on the underlying layers of film. Thus the heat treated area about the trailing edge is the only area that provides the sole means for securing the film to itself and containing the articles on the pallet. If the trailing edge comes loose, the film will be subject to immediate loss of tension and unwrapping.
However, conventional palletizing approaches result in a variety of problems. For example, when palletized materials are stacked one upon the next, there is a tendency for the stack to lean. Further, the runners of an upwardly-disposed pallet sometimes indent or distort the packaging of the materials. Nails utilized with wooden pallets may also damage the materials during handling.
In response to these and other problems, another form of palletizing, sometimes referred to as “slip sheet” palletizing”, was developed. A slip sheet has a load-bearing surface on which materials (e.g., rolled absorbent materials for use in an absorbent article) are capable of being stacked vertically. With the slip sheet approach, materials are stacked on each other, but have a thin slip sheet positioned between adjacently stacked materials. Despite its benefits, however, slip sheet palletizing still possesses various problems, particularly for soft and flexible materials. For instance, when stacking multiple materials, the increased weight causes the entire stack to lean slightly. Even if the stack does not fall, the leaning imparts increased pressure to the outer edges of the materials. When the material is relatively soft and flexible, this increased pressure can cause the outer edges to be indented and deformed, which is obviously undesired. In many instances, these deformed materials must actually be discarded.
Additionally, the use of slip sheets produces additional waste material at the site of unloading the pallet. The personnel that are charged with unloading, or unstacking, the materials stacked upon the pallet, must remove and dispose of the slip sheets. The removal of the slip sheets can cause a decrease in efficiency due to the additional time required to remove the slip sheet as well as time to either stack the slip sheet with other slip sheets removed from the un-palletizing operation, or to dispose of the slip sheet. Further, slip sheets are usually not recycled for further use and usually end up as landfill material. Clearly, the use of slip sheets in current palletizing operations is a necessary evil. While the slip sheets are functional to provide a pallet of stacked materials with necessary stability, the end result of the use of slip sheets is clearly a time and environmental liability.
As such, a need currently exists for a system and method for more effectively stacking materials to provide a pallet of stacked materials with the needed stability for shipping, eliminate any un-needed or unnecessary steps at unloading, and reduce, or eliminate the amount of land-filled material. This can be particularly problematic with the palletizing of relatively soft and flexible materials.